(13)C isotopic signature and C concentration of soil density fractions illustrate reduced C allocation to subalpine grassland soil under high atmospheric N deposition
| Autor: | Matthias Volk, Seraina Bassin, Moritz F. Lehmann, Christian P. Andersen, Mark Johnson |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
chemistry.chemical_classification
Canopy geography geography.geographical_feature_category 010504 meteorology & atmospheric sciences δ13C Chemistry Bulk soil Soil Science 04 agricultural and veterinary sciences 01 natural sciences Microbiology Bulk density Grassland Article Soil respiration Isotopic signature Environmental chemistry 040103 agronomy & agriculture 0401 agriculture forestry and fisheries Organic matter 0105 earth and related environmental sciences |
| Popis: | We followed soil C fluxes in a subalpine grassland system exposed to experimentally increased atmospheric N deposition for 7 years. Earlier we found that, different from the plant productivity response, the bulk soil C stock increase was highest at the medium, not the high N input as hypothesized. This implies that a smaller N-deposition rate has a greater potential to favor the biological greenhouse gas-sink. To help elucidate the mechanisms controlling those changes in SOC in response to N deposition, we produced four soil density fractions and analyzed soil organic C concentration [SOC], as well as δ(13)C signatures (δ(13)C(SOC)) of SOC components. Soil respired CO(2) (δ(13)C(CO2)) was analyzed to better distinguish seasonal short term dynamics from N-deposition effects and to identify the predominant substrate of soil respiration. Both at the start of the experiment and after 7 years we found a strong, negative correlation between [SOC] and δ(13)C(SOC) of the soil density fractions in the control treatment, consistent with an advanced stage of microbial processing of SOC in fractions of higher density. During the experiment the [SOC] increased in the two lighter density fractions, but decreased in the two heavier fractions, suggesting a possible priming effect that accelerated decomposition of formerly recalcitrant (heavy) organic matter pools. The seasonal pattern of soil δ(13)C(CO2) was affected by weather and canopy development, and δ(13)C(CO2) values for the different N treatment levels indicated that soil respiration originated primarily from the lightest density fractions. Surprisingly, [SOC] increases were significantly higher under medium N deposition in the |
| Databáze: | OpenAIRE |
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